The known generation apparatus for dissolving gas in liquid often uses diffuser or Venturi tube for assisting the process. FIG. 1 shows a schematic view of the structure of a known apparatus using diffuser. As shown in FIG. 1, the apparatus includes a high-pressure gas tank 11, a dissolving tank 12 and a diffuser 13 disposed in the tank 12. The dissolving tank 12 further includes a liquid inlet tub 121, a fluid outlet tube 122 and a gas venting tube 123 for allowing the liquid to enter the dissolving tank and outputting a high density gas-liquid solution. The high-pressure gas tank 11 is connected to the diffuser 13 through a gas tube 14. The diffuser 13 allows the entering gas to generate a large amount of tiny bubbles. By increasing the contact area between the tiny bubbles and the liquid, the dissolving efficiency is increased during the bubble surfacing time to obtain a high density gas-liquid solution. When the gas inside the dissolving tank 12 to much or the pressure is too high, the un-dissolved gas can be vented out through the gas venting tube 123. However, known disadvantages of the above apparatus include the following:
1. The bubbles, after surfacing above the liquid level, cannot be recycled and reused.
2. To keep the bubbles remain in the liquid long enough for improving the dissolving efficiency, the dissolving tank must be sufficiently deep, which would take up much space.
FIG. 2 shows a schematic view of the structure of a known apparatus using Venturi tube. As shown in FIG. 2, the Venturi tube 21 includes a liquid inlet tube 211, a liquid outlet tube 212 and a gas inlet tube 213. The liquid inlet tube 212 is connected to a liquid transmission tube 22 and a pump 23 so that the liquid can be transmitted into the Venturi tube 21. The gas to be dissolved in the liquid enters through the gas inlet tube 213 to be mixed with the liquid. The theory behind the above apparatus is: using the high speed jet current generated by the high-pressure liquid entering the throat of the tube with a smaller diameter to cause negative pressure to suck the gas into the tube throat for mixing with the high-speed jet current and flowing out a solution with dissolved gas. The known disadvantage is the above apparatus is that the amount of gas is restricted by the liquid flowing speed. As such, the range for adjustment is limited, the generated bubbles are often bigger and the contact area is smaller, leading to less efficiency.